Is measurement of serum thyroglobulin at the time of 131I remnant ablation after thyroidectomy useful for early prediction of recurrence of differentiated thyroid carcinoma?

Abstract

Context: The follow-up of differentiated thyroid cancer (DTC) after total thyroidectomy is commonly based on serum Tg determination, 131-iodine ((131)I) diagnostic whole-body scan (WBS) and neck ultrasound (n-US). Aims: Assess the frequency and risk factors for recurrence and persistent disease in patients with both undetectable serum Tg level and normal post ablation WBS at the time of ablation. Settings and Design: We conducted a retrospective study of 500 consecutive DTC patients, treated with I-131 between January 2000 and January 2009. Methods and Materials: Patients were treated in all cases with a 131-I activity. Serum Tg level was measured on the day of I-131 administration. A neck scintigraphy was performed in all patients. Statistical Analysis Used: It included a descriptive study with, for qualitative variables, a calculation of absolute and relative frequencies. Quantitative variables were expressed as averages, medians, and standard deviations with extreme values. Results: Among 500 patients ablated, 100 consecutive patients were included. The WBS was abnormal in 5 and n-US abnormal in 1. Among 95 patients with a normal WBS, Tg/TSH 6-18 months after ablation was undetectable. n-US was normal in 92 and falsely positive in 3. After a mean follow-up of 5 years, recurrence occurred in 2 cases, both with an aggressive histological variant. Conclusions: Our data suggest that the presence of undetectable levels of serum Tg/TSH at the time of the first control WBS after initial treatment, is highly predictive of complete and persistent remission. The control WBS has never given information that could influence the following therapeutic strategy. On this basis, we propose that the diagnostic (131) I WBS may be avoided in patients with undetectable levels of Tg/TSH in the absence of TgAb at the time of ablation.